Tone arm



Aug. 28, 1923. I 1,466,140

A. K. MILLER TONE ARM Filed Feb. 5, 1921 fizz/6 7% 7W fined 1(MLZZ6/7 Patented Aug. 28, 1923.

. UNITED. STATES ALFRED K. MILLER, or LosANGELnsj CALIFORNIA.

TONE ARM.

* Application fi1ed'February5, 1921. Serial No. 442,641.

I To all whom it may concern:

v Be it known that I, ALFRED K. MILLER, a citizen of the United States, residing at Improvements in Tone Arms, of which the following. is a specification.

This invention relates to devices and apparatus of the general character that is used as, and is generally known as, the tone arm of a phonograph mechanism; so, for the purpose of clearly describing and illustrating my invention, I shall consider a specific form of the invention which is particularly designed as a tone arm for a phonograph, but it will he distinctly understood that I do not thereby limit my invention to such par ticular use. In its broader aspects my invention may be considered to be a sound transmitting and modifying apparatus.

Considering thus myrinvention as applied to tone arms (withoutany implied. limitation of the invention thereto) it maybe stated preliminarily thatone of the objects of the invention is to provide a tone arm construction that will amplify sounds coming from a phonograph reproducer; will amplify and expand the sound withoutin- .troducing into it foreign vibrations; of any objectionable character willtran-smit the sound from the reproducer, in its original purityyand will,'without materially altering the character or quality of the tones produced by the reproducer, somewhat qualify those tones, so as to eliminate from those tones certain somewhat undesirable features. This elimination of certain undesirable featuresor qualities of the tone coming from the reproducer applies more particularly to ordinary reproducersthan to my reproducer I of theicharacter shown in the accompanying drawings. In an ordinary L reproduccr as .used in present phonographs, there is always a tendency for certain tones or" sound to blare out; that is, to be reproduced. with such force and volume as ,to practically drown out the accompanying sounds. This objectionable feature has been .to a very large extent'elimina tcd in my .reprodncer; but the tonearm itself,has,-as will be explained, the quality of covering tones which would otherwise be produced ina blaring fashion.

There are other objects of the invention; but they,-together with the foregoing 0bj ects, will be better understood from thefollowing detailed description of specific forms l which Los Angeles, county of Los Angeles, State of California, have invented new and useful at 15,. such as soft felt.

of my invention, referenceflfor that purpose being had tothe Fig; 1 is a plan of my improved tone arm,

showing a reproducer in connection therewith and showlng the connection of a tone arm of the phonograph; Fig.2 is a horizonv tal longitudinal section of the same; Fig. 3 .1s a similar horizontal longitudinal section showing a slightly modified arrangement;

Fig. 4 is. a section showing my improved reproducer whichis here shownin connection with the tone arm, and Fig. 5 is an en larged detail sectiontaken as indicated by line 5- 5 on Fig. 2. 1

' In the drawings the numeral 10 may generally designate the upper end of the horn of the" instrument, this upper end of the horn being provided with ahorizontally swinging swivel which turnson the center pivot 11. To provide arrangements so that the reproducer: may follow the vertical undulations or inaccuracies of a phonograph record, I prefer in my construction to place the freely vertically movable oint or section at the rear of the tone arm rather than between the tone arm and the repro'ducer; so that the reproducer ismounted more directly, and without the interposition of a numberof'movable joints, or any loosely movable joint, in its connection with the forward end of thetone arm. Accordingly, in

my present arrangement the upper end of the horn, or the swivel thereof, has a cup-shaped flange 12 within which a collar 13 fits somewhat loosely, the collar being mounted in the flange on a pair of pivots 14, as is clearly illustrated. These pivots are on a horizontal pivot'line, so that the tone arm, whose rear end; is mounted in the collar 13, may raise and lower slightly. Betweenthe end of the collar 13 and tl1e.;flange 12 Linterpose a washer of some Suitablesoft material as This washer substantially fills up ,the otherwise open space at that point, at the-same time is soft enough toallow the slighttilting motion necessary for, the. reprodulcer to raise and lower in following the. vertical undulations which. are usually present in any ordinary phonograph tothe carrier table not being absolutely true. Referringfir'stto Figs. 1, 2 and 5, it will be seen that the tone arm proper comprises an outer cylindrical shell 20,- comparatively accompanying drawings, in

record, due to suchphonograph records not being absolutely true and flat disks, or due long. This shell is preferably rather heavily walled; and I find that ordinary brass tubing, with rather heavy walls, is suitable for the purpose. It is not intendedthat the walls of this shell be vibratory or resonant; but it is rather intended that they be solid. Shell 20 is mounted in .the collar 13 at its rear end. At its forward end it receives and supports the forward end of interior-sound modifying member 21 and also supports the reproducer R, In the form shown in Figs. 1, 2 and 5 the elbow 22, upon which thereproducer If is mounted, extends into the for- 'ard end of the hollow sound n'iodifymg member 21, and is rotatable therein, from the position indicated in Figs. 1 and 2 to a position where the elbow extends upwardly rather than horizontally. This swinging movement is limited by a pin and slot arraiigement, as indicated at 2 3, so that the reproducer may be rotated around the hOI'IZOII- tal longitudinal axis of the tone arm to an angle of about 90. This relative movement of the reproducer allows the reproducer to be raised from a record for changing records and for changing needles. The horizontal arm of elbow 22 fits in. the forward end of hollow sound modifier 21 with a fairly tight friction, so that although it may be turned by hand from one position to' the other, there is no looseness at the point. The reproduccr, mounted upon the elbow 22, fits upon that elbow with a fairly tight joint, so that there is no looseness at that point. Thus as will be referred to hereinafter, there are no loose joints between the reproducer, or between the vibrating sound producing parts of the reproducer. and the forward end of the tone arm and sound modifying member 21.

The sound waves which pass through elbow 22 from the reproducer are delivered into the forward end of hollow sound modifying member 21. This resonating member is. in the preferred form. of construction shown in the drawings and herein explained,

supported. at its forward end only in exterior shell 20. Exterior shell 20 is preferably cyliiulrical; that is it is preferably of the same size throi'ighout and preferably circular in cross section although its cross sectional confi uration can be madeother thancircular. The sound modifying meu'iber 2.1 is also, correspondingly, circular in cross section, so that it may be arranged concentrically with relation to shell 20.. Sound modifying member 21 may preferably be constructed of fibre, wood. or bakelite or some suitable material of like nature suitable to be resonantly vibratory without having the character- 'istic metallic quality of a thin metallic vibratory tube or tongue or the like. Thus, for instance. I make the sound modifier 21 of as suitable hard ,fibre. or hard wood. throughout most of its length it has a relatively thin cylindrical wall 25, which wall is, at the forward end at 26, expanded so as to fit tightly into shell 20. Throughout part of its length, preferably through most of its length, the wall 25 has one or more slots 27 cut through it. For instance it may have two opposite longitudinal slots as shown in the drawing. These slots may or may not extend to the rear end of the tube; but in my present preferred construction I prefer to have them stop somewhat short of the rear end of the sound modifying tube; and the rear end of the resonating tube is choked down somewhat as is illustrated at 28. Other than this slight closure or choke the hollow interior of the sound modifying tube is of the same size throughout its length. Also, preferably, although not necessarily, the exterior surface of the sound modifying tube wall, is truly cylindrical; so that the annular space between the sound modifying tube and shell 20 is of the same size throughout its length.

IVithout attempting to limit myself to the particular proportions and conformations herein shown and described. I may say that, as a typical instance, I obtain very good results from a device built substantially in accordance with the drawings herewith; which drawings are approxin'iiately to proportion ate. scale; and the length of shell 20 being about SlX inches and its outside diameter one and one-half inches and the thickness of its wall one-sixteenth of an inch; the ex terior diameter of the sound modifying tube being one and one-eighth inches and the thickness of the sound modifying tube wall being about one-sixteenth of an inch; the sound modifying tube being constructed of what is known as hard fibre. Its length is about five and one-half inches. The inside diameter of the choked end is about fifteensixteenths of an inch.

In actual operation I find that a tone arm constructed in accordance with my present invention gives very markedly improved results. The sound is transmitted without in trusion of undesirable foreign sounds. Amplification is caused by the tubular sound modifying member. At the same time, the closed end of the resonating member has the effect of covering those sounds which would otherwise blare out. And I find that the resonating or amplifying effect is presentover a wide range of sound pitch and tone quality.

Now another feature of the general ar rangement herein illustrated and described is the feature which eliminates loose joints between the vibratory parts of the reproducer and the tone arm. In the usual phonograph construction, there are comparatively loose connections between these two parts: and the looseness causes a certain amount. of loose vibration, introducing into the final reproduced sounds a great many undesirable noises. The construction herein shown and described, as will be understood from the foregoing description, is very simple and involves only. one tightmovable joint between the reproducer and the tone arm, that movable joint being the one about which the .reproducer is turned about ahorizontal axis.

The joint of the reproducer itself to the elbow 22, although it is removable, is also tight, as it is not ordinarily moved from time to time. Furthermore, in my particular form of reproducer herein illustrated, (and which is the subject-matter of my application, Serial No. 359,725, filed February 18, 1920, for phonograph reproducer) the mounting neck which is mounted on the elbow 22 is formed as an integral part of the member which also forms the vibrating diaphragm 31. In fact, through this method of mounting, the vibrating diaphragm 3i becomes the supporting means for the case parts of the reproducer R. The case of this reproducer carries the primary diaphragm 32, which is mounted substantially parallel to and close to the secondary diaphragm 31. On the opposite side of the primary diaphragm. 32 there is an enclosed resonating space S twhose proportions are gaged and designed so as to form an air resonating chamber to resonate and qualify the vibrations of primary diaphragm 32. Primary diaphragm 32 is vibrated through the medium of needle arm 35 from the needle 36. The mounting of theneedle need not be herein specifically described. The feature which I wish to bring out in rela tion to the reproducer is that there are no lOOSely movable parts in the system between the vibrating parts of the reproducer and the forward end of the tone arm. I

In Fig. 3 there is shown a somewhat moditied form of the tone arm in which the re producer makes connection directly into the side of the front end of the-tone arm instead of into the end. Here in Fig. 3 a straight nipple 22 replaces the elbow 22, this straight nipple extending through the wall 26 of resonating tube 21 and also through the wall 40 of the swivel member 41 which forms a swiveling extension of shell 20. Extension 41 is mounted tightly but revolubly on shell 20 and a pin and slot arrangement at 23 limits the swiveling movement to the same quarter revolution as hereinbefore explained. modifying member is mounted in member L1 and in this case turns with the member ell when the reproducer is turned for raisin or lowering.

aving described a preferred invention, I claim 1. In apparatus of the character described, a tubular outer shell, and a tubular form .of my The tubular sound outer shell and said open end being somewhat choked.

2. In apparatus of the character described, a tubular outer shell, and a tubular sound modifying member extending freely longitudinally through the outer shell and substantially concentric therewith, and de.

fining an annular space betweenit and the outer shell, said tubular sound modifying member being longitudinally slotted through its wall with a plurality of slots circumferentially spaced from each other.

3. In apparatus of the character described, a tubular outer shell, an inner tubular sound modifying member extending lengthwise through the shell and supported in the shell at one end only, the remainder of the sound modifying member being spaced from the inner wall of the shell to define an annular space between it and the shell, the free end of the sound modifying member being somewhat choked but other wise open to the interior of the shell, and

sound modifying member extending freely longitudinally through the shell and defining an annular space between it and the outer shell, said tubular sound modifying member having an open end within the shell and said end being somewhat choked, and the wall of the tubular sound modifying member being longitudinally slotted.

5. In apparatus of the character de scribed, a tubular outer shell, and a tubular sound modifying member extending freely longitudinally through the shell and defining an annular space between it and the outer shell, said tubular sound modifying member having an open end within the shell, andthe wallof the tubular member being slotted with anelongated slot longitudinal of the member.

6. In apparatus of the character described, a tubular outer shell of metal and having relatively thick and heavy walls, and a tubular sound modifying member extending freely longitudinally within the shell and composed of a non-metallic substance.

Inwitness that I claim the foregoing I have hereunto subscribed my. name this 31st dayof January, 1921.

ALFRED K. MILLER. 

